Defusable Clock

The Defusable Clock kit is NOW AVAILABLE FOR PURCHASE!

This may look like a dangerous device, but it’s really just an ordinary alarm clock — with a twist.


I thought it would be fun to build an alarm clock that looks just like the type of bomb that we always see in Hollywood movies. I certainly don’t know anything about how a real bomb might look, but in the movies they always have sticks of dynamite strapped together, a red digital readout, and a bunch of curly wires. Instead of just building an ordinary clock, I thought it should have a detonation sequence with a scary countdown just like in the movies. And why not make it “defusable” so I an try to stop the countdown by cutting the correct wire?

The Defusable Clock is a fully-functional alarm clock just like you’d expect (a normal beeping alarm, snooze alarm, etc.). But at any time you can press the big red button to start a scary countdown sequence exactly like bombs in Hollywood movies. There are 4 wires across the top of the clock. You have 10 seconds to choose the correct wire to cut: one wire stops the countdown and saves the day, two have no effect, and one will “detonate” the device immediately. These role of each wire is randomly assigned when the detonate button is pressed, so it’s a new challenge every time. Also, the wires are attached with screw terminals, so you can replace them easily. If you don’t want to actually cut the wires, you can just pull them out of the screw terminals if you keep the screws a little loose.

The microcontroller is an ATmega328 with the Arduino bootloader, so this clock is programmable with the Arduino IDE. The ATmega328 is certainly more powerful than needed for a clock, but this device has lots of inputs/outputs, and ATmega328 chips are now about the same price as the older ATmega168. It keeps very accurate time and requires a simple 9V “wall wart” power adapter. A special alarm mode lets you even use the countdown sequence as the alarm and require it to be defused when you wake up in the morning. What a stressful way to start the day!

We are going to offer this as an electronics kit later this fall. Only the electronics will be in the kit — nothing that looks like dangerous explosives! With some imagination, I’m sure you can make a great looking Defusable Clock for yourself, but don’t go scaring anyone with it, and don’t bring it anywhere near an airport, ok? The product page will have plenty of warnings not to use this kit for any evil purposes or get into trouble with your school, employer, or local law enforcement! There will also be a picture gallery where you can submit a picture of your clock after you build it.

UPDATE: the Defusable Clock kit is NOW AVAILABLE FOR PURCHASE!

I’m sure some of you will have some ideas and comments, so please leave them below. Keep in mind that this is no more dangerous than any other alarm clock, and yes, we have already spoken to a lawyer about all of this.

Here’s one more version I made using clay for plastic explosives:

Clay used to simulate C4

Published by Michael, on September 5th, 2011 at 7:06 am. Filed under: Arduino,Art. | 108 Comments |

108 Responses to “Defusable Clock”

  1. Im just wondering what you used to run the files for the schematics for this kit

    Comment by Jacob on March 20, 2012 at 8:55 AM

  2. Jacob: I use Cadsoft Eagle.

    Comment by Michael on March 20, 2012 at 9:13 AM

  3. thanks, though where would one go to get that to open the files if it isn’t on the computer that they are using? also, do you think that this is a good project to do for a project at school?

    Comment by Jacob on March 22, 2012 at 7:26 AM

  4. Um, you could google “cadsoft eagle”.

    Do I think *what* is a good project to do for a school project? I have no idea what you are thinking.

    Comment by Michael on March 22, 2012 at 8:14 AM

  5. with the hack system, could you hack it to close a lock after the timer expires? got the idea after reading about the person with the 4 bombs and the cupcakes

    Comment by Jacob on March 22, 2012 at 7:30 AM

  6. Yes, you could do something like that by modifying the software. I have no idea who the person with the 4 bombs and the cupcakes is….no idea what you are talking about.

    Comment by Michael on March 22, 2012 at 8:16 AM

  7. As a retired fire chief I see the “Bomb” as a necessity for my 10 yr old grandson (he’s a ham operator) to build when he visits June 23–July 2 (’12). Would it be possible to have you program one for 30 seconds’ countdown and send it by then? I can Paypal or credit card immediately on your reply.

    Looking for your prompt reply — my cell is 406 660-0195, email is Sorry for the rush, just saw it in a Popular Science tonight. (The 10 second countdown looks too short for a young lad to wake up and respond in time!) Love the idea, just fits this family’s humor profile!

    Roy C

    Comment by Roy Cornell on May 30, 2012 at 8:38 PM

  8. Disregard the request for 30 second countdown, I see now that the countdown time is adjustable, ordering one now!

    Roy C

    Comment by Roy Cornell on May 30, 2012 at 8:47 PM

  9. Hello,I am really interested and want to buy one.
    But I come from China. How can I buy one?
    Thank you very much.

    Comment by Nancy on June 17, 2012 at 12:13 PM

  10. Hi. Unit arrived today and I copied the wiring from the pictures above and all works well EXCEPT for the alarm. Yes I’ve made sure I’m using the pm/am in the right way but no sound? Any suggestions. I’m sure it’s operator error. Also I read in the blog above aparently the detonator time is adjustable, and the alarm can be changed from “normal” or “detonator” can you please explain how. No operating/adjusting instructions came with the unit. Are they available online? Many thanks, great novelty. Looking forward to your reply. Scott R, Sydney Australia.

    Comment by Scott on September 11, 2012 at 3:37 AM

  11. Forget my last. I just found the operating instructions. Cheers scott R

    Comment by Scott on September 11, 2012 at 3:54 AM

  12. Forget my last. Just found the operating instructions. Situation resolved. Cheers Scott R

    Comment by Scott on September 11, 2012 at 3:56 AM

  13. Hello Michael,

    PERFECT!!!! EXACTLY WHAT I WAS LOOKING FOR!!! Just like JERRY (Posted in 02/27/2012), I too was looking for a mock bomb for my AIRSOFT Games. I don’t have Sponsers quite yet, because I’m just starting out… But I LOVE THIS PROJECT!! Nice job! :-)

    If I order one… could you do just ONE simple program?? Can you eliminate the cable that detonates? I know we can program it ourselves, but I’m just not that technically savy… but I can build some sick props though!! I’ll send you some pics once I have it done! :-) Also…I too want to make buzzer louder so all the players know when the bomb is being activated or detonated. But I have other ways of making that happen. :-) Please email me when you have a sec… Im sure you have LOTS of emails to reply to.

    Thanks again in advanced!! GREAT PROJECT!! LOVE IT!! :-)

    Comment by Sevenvibes on October 12, 2012 at 8:46 PM

  14. Yeah, no problem to make small program changes. I do lots of code customizations for Airsoft teams. Just email with your change requirements and I can do that. Glad you are excited — I sell a lot to Airsoft/Milsim teams.

    Comment by Michael on October 12, 2012 at 9:01 PM

  15. Oops… meant to say I want to make it louder so all my players (in close quaters AIRSOFT games) can hear when the bomb is ACTIVATED, DETONATED, and DEFUSED. :-)

    I’m also going to cut the wires, and solder Female and Male RCA plugs for the DIFFUSAL “sequence”. (Players can just pull the wires instead of actually cutting them).

    Thanks for creating this!! JUST what I was looking for!! I’m excited to get it and start using it in my AIRSOFT games!! :-) Hope to hear from you soon!

    Comment by Sevenvibes on October 12, 2012 at 8:50 PM

  16. I’m interested in purchasing the “sticks of dynamite” defusable alarm clock, but I can’t find it in your product list. Are you out iof stock or no longer selling that one?

    Comment by Denise on December 10, 2012 at 7:56 AM

  17. We do NOT ship phony bomb parts. We only sell electronics.

    Comment by Michael on December 10, 2012 at 8:03 AM

  18. I purchased the assembled kit from solderbot and it is absoluteley incredible. However I have no knowledge of soldering or any of that stuff so I was wondering if you could point me to instructions or explain to me how to make the clock run off of batteries (ie the 6 D-Cell setup suggested for people who want to try battery operated). Please email me! Thanks!!

    Comment by Anthony on December 22, 2012 at 12:01 AM

  19. Just connect 6 D cells in series to get 9V. 6 times 1.5V = 9V. On the DC power connector on the clock, the solder joint directly beneath the connector is the ground (-). The soder joint just behind the end of the connector is the +9V connection.

    Comment by Michael on December 22, 2012 at 8:19 AM

  20. Hey, I need instructions on how to assemble the clock!

    Comment by dave craton on February 21, 2013 at 1:49 PM

  21. The link should be printed right on the bag.

    Comment by Michael on February 21, 2013 at 2:04 PM

  22. See full product details or use the support forum to get help.

    Comment by Michael on April 7, 2013 at 8:06 AM

  23. when will Defusable Clock – Assembled Electronics be back in stock?

    Comment by Rico on April 11, 2013 at 1:00 AM

  24. the timer for the explosion only for 10 second? can it set into 2 minute or more?

    Comment by Dede on May 15, 2013 at 2:19 AM

  25. Yes, see the usage instructions:

    Comment by Michael on May 15, 2013 at 9:15 AM

  26. I purchased you Defusable clock and was wondering do you happen to have template of layout display, buttons and lighting as I was going to laser cut a faceplate for mine, if not no real big deal but would save me one step.

    Also I noticed you can pre program units for airsoft

    Thanks Donald

    Comment by Donald Ethredge on June 12, 2013 at 12:53 PM

  27. I’m afraid I don’t. You can use the board image from and scale it to 3.4″ x 2.9″. That may help.

    Comment by Michael on June 12, 2013 at 3:36 PM

  28. Hi , the defusable clock went together great with excelent instructions and went 1st go. The neighbors seen it and they want one too.I printed a label “Dairschegoes Industries Pty Ltd DYNAMITE,DANGER Rediculously Explosive”. Any deals on multiple orders?
    Thomas ,Australia.

    Comment by Thomas Rosenzweig on June 21, 2013 at 4:17 AM

  29. Maybe a discount. Please contact us with the “Contact Us” link in the store.

    Comment by Michael on June 21, 2013 at 8:07 AM

  30. Looking for one for paintball scenario

    Comment by don on August 25, 2013 at 6:11 PM

  31. If I’m not mistaken this clock was just used as a prop on the TV show “The Blacklist: Pilot s01e01”.

    Comment by npc on September 29, 2013 at 12:41 PM

  32. I have altered one of your photos of this excellent device. I made an animated GIF where the display blinks 12:00. It’s on Flickr; let me know whether the attribution is appropriate.

    I THINK Flickr will show you the animation at this URL. Seems to be tricky to get it to display animated GIFs.

    Comment by Bill Higgins-- Beam Jockey on January 22, 2014 at 10:45 AM

  33. I am curious to find out what blog platform you’re using?
    I’m experiencing some minor security issues with my
    latest blog and I’d like to find something more safe. Do you have any recommendations?

    Comment by avtex on May 24, 2014 at 5:59 AM

  34. It says right at the bottom of the page. “Powered by WordPress”

    Comment by Michael on May 24, 2014 at 8:38 AM

  35. I blog quite often and I genuinely appreciate your content.
    This article has really peaked my interest. I will bopk
    mark your website and keep checking for new information aboiut once per week.
    I subscribed tto your Feeed as well.

    Comment by right hybrid bike on October 15, 2014 at 11:07 AM

  36. Is there a way to amplify the sound or connect a bigger speaker so I can use it on airsoft games?

    Comment by lifes26 on October 19, 2014 at 4:13 AM

  37. Yes, some Airsoft people use the trigger output to turn on a relay which drives a siren. I have a Radio Shack siren that is very loud and that works well.

    Comment by Michael on October 19, 2014 at 7:23 AM

  38. Just don’t bring it to school with you.

    Comment by Paul Callahan on September 21, 2015 at 2:25 PM

  39. sir i want to make this defusable at hme for my project so plz give me whole instruction and material i wil require and als the coding .

    Comment by Ashvini on March 15, 2016 at 11:32 PM

  40. Hi.
    Could I use a tilt switch instead of the red button?
    Also, do you have to cut the wires in any particular order?

    Comment by Mik on May 13, 2016 at 5:44 AM

  41. Yes, you could use a tilt switch. It would need to be closed, then opened to start countdown. See product docs here:

    Comment by Michael on May 13, 2016 at 7:25 AM

  42. Is it possible to add additional posts/wires? I would like to make a puzzle where you have to clip up to nine wires in a specific sequence. If the sequence is not correct: alarm. If correct: clock stops. Is the hardware capable of this?

    Comment by Spanky on January 17, 2017 at 7:58 AM

  43. Sorry, there are only 4 wire inputs. The microcontroller does not have more inputs.

    Comment by Michael on January 18, 2017 at 8:24 PM

  44. wow so beautiful

    Comment by timmaustin on November 14, 2017 at 12:51 PM

  45. Hi Michael

    Can you build/supply a defusable clock that can also subtract time from the clock if the wrong wires are removed or cut, say 5min per wire and add say 4 more coloured wires?


    Comment by Riaan Stadler on February 13, 2018 at 8:48 AM

  46. We offer custom coding as an item in our store. No, more wires cannot be added, it only supports 4.

    Comment by Michael on February 13, 2018 at 8:52 AM

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